The invention relates generally to a system and a method for monitoring electrical machine component integrity and more specifically to a fiber optic based system and method for monitoring end winding components of a rotating machine.
Rotating machines such as electric generators driven by steam turbines or gas turbines have the capacity to carry several thousand amperes of current in their stator windings. Stator windings generally comprise conductive bars secured in corresponding slots in a stator core and end windings extending beyond the stator core for making connections between the conductive bars. End-winding components are subject to electro-dynamic and mechanical forces that induce a displacement of the end windings.
Loosened end winding components rub against each other due to electromagnetic forces that cause wearing of the winding insulation material. Thus, dusts such as glass, mica, resin, and paint may accumulate on the end winding components and may mix with generator oil to form grease near the end windings and other end winding components. The grease normally has varied color from brown to dark, determined by mixing ratio of the dust and generator oil mists. In some circumstances, unplanned outages of generators are needed to clean the end windings, or to replace the damaged insulation protection layer on end windings. The unplanned outages reduce the power system availability and increase unnecessary maintenance cost.
Generator end winding loosening is primarily diagnosed by visual inspection for the presence of dust. However, visual inspection requires the generator to be taken out of service. An alternative inspection method includes monitoring overall end winding motion, typically by using fiber coupled accelerometers placed in a number of locations on the end winding. Fiber coupled accelerometers, however, do not provide dust monitoring functionality and must be positioned at a number of locations (typically 6). Another potential inspection method is based on a camera imaging method, but it is difficult to access all the end winding locations.
Therefore, there is a need for an improved electrical machine component monitoring system to address one or more of the aforementioned issues.